300-415 Question #277: Real Exam Question with Answer & Explanation

Question

Options

• AThe gateway WAN Edge router DPI engine accepts the DNS query for SaaS applications, and DNS queries for noncloud applications follow the explicit path.
• BThe WAN Edge DPI engine never selects a subperforming DIA circuit for the first application, and the WAN Edge router finds the SaaS application.
• CExisting flows change the path and drop the traffic when the performance of the chosen path degrades.
• DApplication traffic flows are routed over best performing DIA circuit, which makes the routing decision based on the best performing path.

Explanation

When a WAN Edge router running dual DIA identifies a cloud SaaS application via DPI, it routes the application traffic over the DIA circuit currently exhibiting the best performance.

Common mistakes.

• A. The DPI engine identifies applications, but the description of how DNS queries are handled for SaaS versus non-cloud applications is not the primary behavior of traffic routing based on performance for identified SaaS apps.
• B. "The WAN Edge DPI engine never selects a subperforming DIA circuit for the first application" is too absolute and does not fully capture the dynamic, real-time nature of selecting the best performing path.
• C. Existing flows changing the path is correct, but dropping traffic when performance degrades is an undesirable outcome; the goal is to move to a better path without significant traffic interruption.

Concept tested. SD-WAN DPI and Application-Aware Routing (AAR) with DIA

Reference. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/sdwan-xe-gs-cr-book/application-aware-routing.html

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